Catalyst for demercaptanization of petroleum distillates

ABSTRACT

The demercaptanization of petroleum distillates may be carried out by means of the oxidation of the mercaptans contained therein using the oxygen in the air, at a temperature of about 80° to about 220° C., in the presence of about 0.01 to about 10.0 mass % of a water-soluble salt of copper, iron, nickel, or cobalt, on a fibrous carbonaceous material in the form of a woven fabric, felt, rope, or twisted strand, used as a heterogeneous catalyst. The fibrous carbonaceous material used in the process contains oxides of calcium, magnesium, copper, manganese, iron, zinc, and aluminum in an amount of up to about 0.03 mass %.

This is a divisional of application Ser. No. 08/313,635, filed Sep. 27,1994 U.S. Pat. No. 5,741,415.

BACKGROUND OF THE INVENTION

The invention relates to the field of the removal of mercaptan sulfurfrom petroleum distillates by means of oxidation, and may be used in theoil refining industry for the demercaptanization of gasoline, kerosene,and diesel fractions.

Methods for the demercaptanization of petroleum distillates are knownwhich involve the oxidation of mercaptans using the oxygen in the air inthe presence of a base and heterogeneous catalysts containingphthalocyanines of cobalt or vanadium deposited onto hard substances,such as activated coal, graphite, alumina, mordenite, silica gel, andothers (see USSR Patents Nos. 355805 and 654180; U.S. Pat. Nos.4,033,860 and 4,481,106).

The principal disadvantages of the indicated methods consist in theinsufficiently high degree of mercaptan oxidation in petroleumdistillates and the significant alkali consumption required by theprocess.

From the point of view of its technical essence and the result obtained,the method which most closely resembles the method described herein isthe method for the demercaptanization of high-boiling-point petroleumdistillates by means of mercaptan oxidation using the oxygen of the air,in the presence of a 5% to 20% solution containing an alkali and aheterogeneous phthalocyanine catalyst, comprising cobalt phthalocyaninein an amount ranging from 0.005 to 0.9 mass %, deposited on acarbonaceous fibrous material in the form of a carbonaceous or graphitefiber.

The principal disadvantages of this method lie in the insufficientlyhigh level of mercaptan oxidation in petroleum distillates, the lowstability of catalytic activity of the catalyst, and the necessity ofconsuming significant quantities of the alkali substance.

SUMMARY OF THE INVENTION

The objective of the present invention consists in achieving an increasein the degree of demercaptanization of petroleum distillates, anincrease in the stability of the catalytic activity of the catalyst, andthe elimination of the necessity of using significant quantities of thebase.

Thus, in accordance with the present invention there is provided amethod for the demercaptanization of mercaptan-containing petroleumdistillates by means of the oxidation of said mercaptans with the oxygenof the air in the presence of a heterogeneous catalyst, said methodcomprising contacting said mercaptans with oxygen in the presence of acatalyst comprising a water-soluble salt of copper, iron, nickel, orcobalt, in an amount ranging from about 0.01 to about 10.0 mass %, whichis deposited onto a fibrous carbonaceous material, said materialcontaining oxides of metals of variable valence; said method beingcarried out at a temperature falling within the range of about 80° toabout 200° C.

Also provided in accordance with this invention is a catalyst comprisinga fibrous carbonaceous material containing oxides of metals of variablevalence, and having deposited on said material, in an amount from about0.01 to about 10.0 mass %, a water-soluble salt of copper, iron, nickelor cobalt.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

According to the method of the invention, the stated objective isachieved by providing a method for the demercaptanization of petroleumdistillates by means of the oxidation of mercaptans using the oxygen ofthe air, in the presence of a heterogeneous catalyst. For the latter,according to this method, a water-soluble salt of copper, iron, nickel,or cobalt may be used, in an amount ranging from 0.01 to 10.0 mass %,deposited on a fibrous carbon material in the form of a fabric-typematerial, felt, or rope, containing oxides of metals of variablevalence, the process being carried out at a temperature ranging fromabout 80° to about 220° C.

For this purpose, a carbonaceous fibrous material is used, containingoxides of calcium, magnesium, copper, manganese, iron, zinc andaluminum, in quantities which provide sufficient basicity for theoxidation of the mercaptans to occur. Typically, this amount will be upto about 0.03 mass %.

The distinguishing features of the proposed method consist in the use ofa heterogeneous catalyst, containing from about 0.01 to about 10.0 mass% of a water-soluble salt of copper, iron, nickel, or cobalt, on amaterial which consists of carbonaceous fibers; the use of acarbonaceous fibrous material in the form of a woven fabric (cloth),felt, or rope (twisted strand), containing the oxides of the abovementioned metals of variable valence in an amount of up to about 0.03mass %; and the performance of the process at a temperature ranging fromabout 80° to about 220° C.

The cited distinguishing features of the proposed method define itsnovelty and significant departure from the methods known in the art atits present technical level, since the application of a water-solublesalt of copper, iron, nickel or cobalt as a catalyst, with acarbonaceous fibrous material in the form of a woven fabric, felt, orrope (twisted strand) containing oxides of metals of variable valencebeing used as the bearer of the catalyst, is not described in theliterature and allows the process of demercaptanization of petroleumdistillates to be performed with a higher degree of mercaptan oxidationunder prolonged use of the catalyst and without the use of a base.

Examples of the water-soluble salts of copper, iron, nickel, and cobaltinclude, but are not limited to, salts of inorganic acids such as thesulfates, chlorides and nitroxides (nitrates) of these metals.Phenylates (i.e., Ph--O--Me--O--Ph where Me is the metal and Ph isphenyl) may also be used. For instance, copper sulfate, copper chloride,copper phenylate, iron sulfate, nickel nitroxide and cobalt nitroxideare useful in the practice of this invention, with copper phenylatebeing particularly preferred because it does not carry over into thedemercaptanized product.

The proposed content of the water-soluble salt of Cu, Fe, Ni, or Co onthe carbonaceous fibrous material in an amount ranging from 0.01 to 10.0mass % is both necessary and sufficient, since with a content of thewater-soluble salt of copper, iron, nickel, or cobalt which is less than0.01 mass %, the required degree of mercaptan oxidation is not achieved.At the same time, the higher limit for the content of a water-solublesalt of copper, iron, nickel, or cobalt (10.0 mass %) is determined bythe adsorptive properties of the carbonaceous fibrous material withrespect to the water-soluble salt of copper, iron, nickel, or cobalt.

The use of a carbonaceous fibrous material containing oxides of metalshaving a variable valence in an amount of up to about 0.03 mass % makesit possible to create a necessary and sufficient basicity of thecatalyst being used, and, as a result, to eliminate the need to rely onthe application of an alkaline substance in the process.

Typical oxides of metals of variable valence which are useful in thisinvention include, but are not limited to, oxides of calcium, magnesium,iron, manganese, copper, zinc and aluminum. Generally, these oxides areconsidered to but water-insoluble or only slightly soluble in water.

Carbonaceous fibrous materials in the form of a woven fabric, felt, orrope (twisted strand), containing the oxides of metals of variablevalence in an amount of up to about 0.03 mass % are industriallyproduced by a process involving the soaking of the material in solutionsof salts of the aforesaid metals, with their subsequent thermaltreatment.

By conducting the process at a temperature ranging from about 80° toabout 220° C., it becomes possible to carry out the oxidation ofmercaptans in petroleum distillates at the temperatures of theirliberation, without preliminary cooling, and, as a result, to increasethe degree of mercaptan oxidation and to reduce energy consumption, aswell as associated energy costs, for the demercaptanization of petroleumdistillates.

The preparation of the proposed catalyst is carried out in accordancewith the known method of soaking a carbonaceous fibrous materialcontaining oxides of calcium, magnesium, copper, manganese, iron, zinc,and aluminum in aqueous solutions of the salts of copper, iron, nickel,or cobalt, at the required concentration, with subsequent drying.

The proposed method has found approbation under laboratory conditions inexamples involving the demercaptanization of a model mixture ofdodecylmercaptan in dodecane, a gasoline fraction (boiling-off range 60°to 180° C.), a kerosene fraction 120° to 240° C.), and a diesel fraction(180° to 350° C.).

The method is illustrated by the following examples.

EXAMPLE 1

Five grams of a heterogeneous catalyst containing 10 mass % coppersulfate on a carbonaceous fabric which further contains oxides ofcalcium, magnesium, copper, manganese, iron, zinc, and aluminum in aquantity of 0.03 mass % are loaded into a batch reactor. The coppersulfate is deposited onto the carbonaceous fabric by the method ofsoaking to saturation using an aqueous solution. Then, 35 ml of a modelsolution of n-dodecylmercaptan in dodecane are loaded into the reactor.

The reactor constitutes a cylindrical vessel made of glass, having acapacity of 100 ml, heated from the outside by a metallic spiral. Air issupplied to the reactor from the bottom; this air is evenly distributedwithin the reactor space due to the Schott filter which has beeninstalled in the lower part of the reactor. The oxidation of themercaptans is carried out with the oxygen of the air, at a temperatureof 100° C. and atmospheric pressure, with air being supplied at a rateof 0.5 l/min. The time of oxidation is 4 minutes.

The mercaptan sulfur content in the starting and refined raw material isdetermined by method of potentiometric titration.

The results of the experiment are presented in Table 1.

EXAMPLES 2-13

The demercaptanization of a model mixture of dodecylmercaptan indodecane is carried out by a method similar to the one described forExample 1. The composition of the catalyst and the results of theexperiment are given in Table 1.

EXAMPLES 14-16

The demercaptanization of a model mixture of dodecylmercaptan indodecane is carried out by a method similar to the one described forExample 1, in the presence of known catalysts. The results of theexperiment are given in Table 1.

EXAMPLE 17

Under the same conditions as those described in Example 1, in thepresence of a heterogeneous catalyst which contained 1 mass % coppersulfate on a carbonaceous fabric containing 0.03 mass % of the oxides ofmetals indicated in Example 1, at a temperature of 220° C., over aperiod of 5 minutes, the demercaptanization of a diesel fraction havinga mercaptan sulfur content equal to 0.02 mass % is carried out. Analysisof the demercaptanized diesel fraction showed the residual content ofmercaptan sulfur to be 0.0005 mass %. At the same time, the degree ofoxidation of mercaptans in the diesel fraction constitutes 97.5%.

EXAMPLE 18

Under the same conditions as those described in Example 1, in thepresence of a known heterogeneous catalyst which contains 0.5 mass % ofcobalt disulophthalocyanine on a carbonaceous fabric (without oxides ofmetals) and a 20% alkali solution, at a temperature of 220° C., over aperiod of 5 minutes, the demercaptanization of a diesel fraction with amercaptan sulfur content equal to 0.02 mass % is carried out. Analysisof the demercaptanized diesel fraction showed the residual content ofmercaptan sulfur to be 0.0075 mass %. At the same time, the degree ofoxidation of mercaptans in the diesel fraction constitutes 62.5%.

EXAMPLE 19

Under the same conditions as those described in Example 1, in thepresence of a heterogeneous catalyst which contains 1 mass % of coppersulfate on a carbonaceous fabric containing 0.03 mass % of the oxides ofmetals described in the example, over a period lasting 3 minutes, thedemercaptanization of a gasoline fraction having a mercaptan sulfurcontent of 0.077 mass % is carried out. Analysis of the demercaptanizedfraction indicated the residual content of mercaptan sulfur to be 0.0001mass %. At the same time, the degree of oxidation of the mercaptans inthe gasoline fraction constitutes 99.87%.

EXAMPLE 20

Under the same conditions as those described in Example 1, in thepresence of a known heterogeneous catalyst which contains 0.5 mass % ofcobalt disulophthalocyanine on a carbonaceous fabric (without oxides ofmetals) and a 20% alkali solution, at a temperature of 80° C., over aperiod of time lasting 3 minutes, the demercaptanization of a gasolinefraction with a mercaptan sulfur content of 0.077 mass % is carried out.

Analysis of the demercaptanized fraction demonstrated the residualsulfur content to be 0.028 mass %.

At the same time, the degree of mercaptan oxidation in the gasolinefraction constitutes 63.6%.

                                      TABLE 1                                     __________________________________________________________________________                               Mercaptans sulfur content                                                Oxidation                                                                          in the raw material, mass %                        Example               time in                                                                            prior to                                                                            after Degree of                              No.  COMPOSITION OF THE CATALYST                                                                    minutes                                                                            purification                                                                        purification                                                                        purification                           __________________________________________________________________________    1    10 mass % copper sulfate on                                                                    4    0.015 absent                                                                              100                                         carbonaceous fabric containing 0.03                                           mass % metal oxides.                                                     2    1 mass % copper sulfate on                                                                     4    0.015 0.0001                                                                              99.8                                        carbonaceous fabric containing 0.03                                           mass % metal oxides                                                      3    0.1 mass % copper sulfate on                                                                   4    0.015 0.0012                                                                              92.2                                        carbonaceous fabric containing 0.03                                           mass % metal oxides                                                      4    0.01 mass % copper sulfate on                                                                  4    0.015 0.0032                                                                              78.2                                        carbonaceous fabric containing 0.03                                           mass % metal oxides                                                      5    1 mass % copper sulfate on                                                                     4    0.015 0.001 93.3                                        carbonaceous fabric containing 0.01                                           mass % metal oxides                                                      6    1 mass % copper sulfate on                                                                     4    0.015 0.0002                                                                              98.7                                        carbonaceous fabric containing 0.02                                           mass % metal oxides                                                      7    10 mass % copper sulfate on                                                                    4    0.015 absent                                                                              100                                         carbonaceous felt containing 0.03                                             mass % metal oxides                                                      8    1 mass % copper sulfate on                                                                     4    0.015 absent                                                                              100                                         carbonaceous felt containing 0.03                                             mass % metal oxides                                                      9    0.1 mass % copper sulfate on                                                                   4    0.015 0.0006                                                                              96.0                                        carbonaceous felt containing 0.03                                             mass % metal oxides                                                      10   1 mass % iron sulfate on carbonaceous                                                          4    0.015 0.0021                                                                              86.0                                        fabric containing 0.03 mass % metal                                           oxides                                                                   11   1 mass % nickel nitroxide on                                                                   4    0.015 absent                                                                              100                                         carbonaceous fabric containing 0.03                                           mass % metal oxides                                                      12   1 mass % cobalt nitroxide on                                                                   4    0.015 0.0007                                                                              95.5                                        carbonaceous fabric containing 0.03                                           mass % metal oxides                                                      13   1 mass % copper chloride on                                                                    4    0.015 absent                                                                              100                                         carbonaceous fabric containing 0.03                                           mass % metal oxides                                                      14*  1 mass % cobalt disulfophthalocyanine                                                          4    0.015 0.0031                                                                              79.5                                        carbonaceous fabric without metal                                             oxides, and 5 ml of 2.5% aqueous                                              solution of caustic soda                                                 15*  0.5 mass % cobalt                                                                              4    0.015  0.00285                                                                            81.0                                        tetrasulfophthalocyanine                                                      arbonaceous fabric without metal                                              oxides, and S ml of 2.5% aqueous                                              solution of caustic soda                                                 16*  0.5 mass % cobalt                                                                              4    0.015 0.0029                                                                              80.5                                        tetrasulfophthalocyanine on                                                   arbonaceous fabric without oxides,                                            and 5 ml of a 20% aqueous solution of                                         caustic soda                                                             __________________________________________________________________________     *Comparative example.                                                    

On the basis of the experimental data presented in Table 1 and inExamples 17 through 20, it can be seen that by carrying out thetreatment process according to the proposed method, as compared to theknown method, it becomes possible to increase significantly (by 15% to35%) the degree of mercaptan oxidation in petroleum distillates, and tocarry out the process without the use of an alkali substance.

The following example illustrates the preservation of high catalyticactivity after prolonged use of the catalyst.

EXAMPLE 21

Under the same conditions as those described in Example 1, in thepresence of 3 grams of a heterogeneous catalyst containing 1 mass % ofcopper sulfate on a carbonaceous fabric which contained 0.03 mass % ofoxides of metals, a kerosene fraction (120+240) originating from thepetroleum refinery of Ryazan, having a content of mercaptan sulfur of0.0082% mass %, is subjected to demercaptanization over a period of 10minutes. The purified kerosene is drained off, and a fresh portion ofkerosene is poured into the reactor and subjected to oxidation. Theprocess is repeated for several tens of cycles. In a similar manner, thedemercaptanization of a kerosene fraction is carried out in the presenceof a known catalyst. The results of the experiment are given in Table 2.

On the basis of the experimental data presented in Table 2, it can beseen that the proposed method, as compared to the known method, achievesa high stability of the catalytic activity of the catalyst being usedunder conditions of its repeated and frequent use, without regeneration.

The indicated advantages of the proposed method as compared to the knownmethod, allow significant improvements to be made in the technical andeconomic indicators of the process in question.

                                      TABLE 2                                     __________________________________________________________________________                           Mercaptans sulfur content in the                                              raw material, mass %                                   Example           Number in                                                                          prior to       Degree of                               No.  CATALYST NAME                                                                              the cycle                                                                          purification                                                                        after purification                                                                     purification                            __________________________________________________________________________    21   1 mass % copper sulfate on a                                                               1    0.0082                                                                              absent   100                                          carbonaceous fabric                                                                        2                                                                containing 0.03 mass % metal                                                               3                                                                oxides       4                                                                             5                                                           22*  1 mass % copper                                                                            1    0.0082                                                                              0.00205  75.0                                         disulfophthalocyanine on a                                                                 2          0.0022   72.9                                         carbonaceous fabric without                                                                3          0.00243  70.4                                         metal oxides, together with                                                                4 . . . 50 0.00281 . . . 0.0036                                                                   65.7 . . . 55.9                              5 ml of a 20% aqueous                                                         solution of caustic soda                                                 __________________________________________________________________________     *Comparative example                                                     

What is claimed is:
 1. A catalyst comprising a carbonaceous material inthe form of a woven fabric, felt or twisted strand containing oxides ofmetals selected from the group consisting of calcium, magnesium, iron,manganese, copper, zinc and aluminum, and having deposited on saidmaterial, in an amount from about 0.01 to about 10.0 mass %, awater-soluble salt of copper, iron, nickel or cobalt.
 2. The catalyst ofclaim 1, wherein the carbon fiber material contains oxides of calcium,magnesium, iron, manganese, copper, zinc, and aluminum in an amount upto about 0.03 mass %.
 3. The catalyst of claim 1 wherein thewater-soluble salt is copper sulfate, copper chloride, copper phenylate,iron sulfate, nickel nitroxide, or cobalt nitroxide.
 4. The catalyst ofclaim 3 wherein the water-soluble salt is copper phenylate.